1. Field of the Invention
The present invention relates to a tack-in apparatus adapted to draw an end portion of weft yarn into a warp yarn opening with an injection air current.
2. Description of the Related Art
There is a related art tack-in apparatus provided on both sides of a woven fabric on a shuttleless loom, and adapted to temporarily retain after weft insertion and beating are carried out an end of weft yarn cut to a required weft insertion length and thereafter tack this weft yarn end in a warp yarn opening with an injection air current. In addition, in the tack-in apparatus in the shuttleless loom disclosed, for example, in Japanese Patent Laid-Open No. 49550/2001 of the applicant of the invention, a weft yarn end gripping unit for temporarily retaining a weft yarn end, and tack-in nozzles for blowing the weft yarn end to the side of a cloth fell with an injection air current and thereby tack in the same are formed in a single nozzle block.
Injection ports of the tack-in nozzles are opened in the side surface of the nozzle block which is opposed to a warp yarn array, and two tack-in nozzles are provided on the discharge side of the cloth fell and on both the upper and lower sides of a position of the height of a warp line which constitutes a weft yarn path when a beating operation is carried out. The tack-in nozzles are communicated on the inner side of the nozzle block with an air passage, which is joined to a regulator and a pressure air source via change-over valves. The opening and closing of each change-over valve is controlled automatically by a control circuit.
In the case of this related art apparatus, the warp yarn in the vicinity of an end portion of the woven fabric is disordered by the injection air diffused from the tack-in nozzles during a tack-in operation, and a space formed between upper and lower warp yarn when the warp yarn is opened varies. Consequently, a weft inserting operation was carried out unstably. There was the possibility that the injection air impinged forcibly upon the warp yarn to cause the same to be broken, and that an uneven woven fabric in which the condition of the portion thereof which was in the vicinity of a selvage thereof and that of a central portion thereof were different was formed. Especially, in a pile fabric, which is greatly influenced by an air injection current due to a low tensile force of pile warp yarn, uneven formation of pile and breakage of pile warp yarn occur. This caused the quality of the fabric to lower.
In order to improve the convergence of the air injection current, upper and lower tack-in nozzels have been inclined toward a warp line, and the axes of the tack-in nozzels have been crossed. However, when the tack-in nozzels are inclined greatly, a speed component toward a warp yarn opening decreases to cause a weft yarn and transfer force during a tack-in operation to lower and the injection air currents to interfere with each other greatly. Consequently, a turblent flow occured to cause the weft yarn transfer force to be lowered.
The invention has been made in view of the above-mentioned circumstances, and provides a tack-in apparatus capable of directing injection air currents toward a central portion of a warp yarn opening at the time for carrying out the tacking-in of a weft yarn end; transferring the weft yarn end reliably and carrying out a tack-in operation; and reducing the turbulence of the warp yarn.
The invention relates to a tack-in apparatus provided with a cutter for cutting weft yarn after the weft insertion is carried out, and tack-in nozzles for folding back an end portion of the weft yarn cut with the cutter into a warp yarn opening with injection air currents, injection ports of the tack-in nozzles being opened in at least one of upper and lower sides of a path which the weft yarn passes by a beating operation, in which apparatus air guides projecting toward the warp yarn opening are formed between the parts of the weft yarn path which are in the vicinity of circumferential portions of the injection ports and the same injection ports. The surfaces of the air guides which are on the sides of the injection ports are inclined toward the weft yarn path as the surfaces extend closer to front ends of the guides.
The injection ports in the invention are formed in a nozzle block provided adjacently to a warp yarn side portion of the cutter. This nozzle block is provided with a slit which is opened in three directions, i.e., toward the warp yarn side, discharge side and cutter side, and which extends along the weft yarn path, and a weft yarn end releasing nozzle opened at an injection port thereof into the slit and blowing the weft yarn end in the slit toward the discharge side of the slit via injection air. Not less than one injection port of the tack-in nozzles is opened in the portions of the warp yarn side surface of the nozzle block which are above and below respectively of the slit, and the portion of the nozzle block which is between the injection port of at least one of the tack-in nozzles and the slit is provided with the air guide.
The tack-in apparatus according to the invention is adapted to bend the air injection currents from the air injection ports toward the weft yarn path owing to a Coanda effect and by the air guides provided on the weft yarn path sides of the air injection ports, increase the air currents flowing toward a central portion of the warp yarn opening, and transfer the end portion of the weft yarn efficiently. Further, it serves to minimize the air injection currents impinging upon the warp yarn to reduce the turbulence of the warp yarn.